The ornamental design for an strandgrab, as shown and described.
FIG. 1 is a front-upper left perspective view of a strand grab showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broken lines are for illustration of the boundary between claimed subject matter and unclaimed subject matter or for illustration of environmental subject matter only and form no part of the claimed design.